In the production of composite materials comprising a substrate having a release layer provided on at least one side thereof, such- as self-adhesive tapes, surface protective sheets, release sheets, etc., the substrate to be used is treated with a release agent in order to facilitate rewinding of a roll or stripping from an adherent surface. Substrates widely employed in these composite materials are polyvinyl chloride-based substrates including a polyvinyl chloride film, a laminate thereof, and a foamed polyvinyl chloride sheet, and paper or a laminate thereof, from the standpoints of excellent heat resistance, weather resistance and mechanical strength.
Conventional release agents applicable to the polyvinyl chloride substrates have been restricted to those comprising condensation type silicones because addition type silicones are inhibited from curing by a stabilizer contained in the polyvinyl chloride substrate. However, since the conventional silicone release layers have low film strength, they are inferior in anti-lock properties, sticking to an adherent through long-term contact therewith, and are hardly peeled off the adherent, or they are transferred to an adherent to cause contamination. Besides, they delaminate due to a plasticizer contained in polyvinyl chloride substrates to easily remove from the substrate simply by light rubbing.